Conversion of hydrocarbon oils



@CL 10, 1939. 1 C, HUFF CONVERSION oF HYDROCRBON OILS Original Filed Jan. 2, 1951 INVENTOR IIIIIIJ f LYMAN C. HUFF BY f ATTORNEY Patented Oct. 10, 1939 UNITED STATES PATENT OFFICE CONVERSION F HYDROCARBON OILS Application January 2,

1931, Serial No. 506,135

Renewed December 10, 1936 3 Claims.

This invention relates to the conversion of hydrocarbon oils and refers more particularly to the conversion of relatively heavy oils into lighter and more valuable products.

The primary concepts of the invention provide an improved process and apparatus wherein relatively heavy oil may be subjected to conversion conditions of temperature and pressure in a primary heating zone, the vapors subjected to reconversion in a secondary heating zone, and the subsequent treatment of reconverted vapors and unvaporized oil from both cracking operations to produce relatively light liquid products, such as motor fuels and relatively heavy liquid residual products, preferably adapted for use as fuel.

In its more specific embodiment, the invention may comprise subjecting relatively heavy hydrocarbon oil to conversion conditions in a primary heating element, introducing the heated products from said primary heating element into an enlarged zone wherein separation of liquid and vapor may be effected, subjecting the vapors to reconversion conditions in a secondary heating element, introducing unvaporzed liquid from said enlarged zone into a stream of reconverted vapors issuing from said secondary heating element, and introducing the resultant mixture into a secondary enlarged zone `or evaporator, preferably maintained under a reduced pressure, relative to that maintained in the primary enlarged zone or separator, withdrawing unvaporized residual oil from said evaporator, subjecting the same to a cooling action, and introducing a portion thereof into a stream of reconverted vapors from said secondary heating element, subjecting the vapors from said secondary enlarged zone or evaporator to fractionation, returning relatively heavy, condensed components of the vapors from said fractionating zone to said primary heating element for reconversion, subjecting the fractionated vapors to condensation and cooling and collecting the resulting distillate and incondensable gas.

As one feature of the present invention, a secondary charging stock, preferably a distillate of lighter nature than the primary charging stock, may be supplied directly to the primary heating element, combining with the primary charging stock and reflux condensate subsequent to the passage of said primary charging stock through the fractionator of the system.

In another feature of the invention, all or a part of the primary charging stock supplied to the system may be rst passed through an absorber where it may be directly contacted with incondensable gas from the cracking system, substantially stripping the gas of any entrained light liquid products. The primary charging stock may be preferably fed from said absorber to a fractionator of a cracking system in which it may be directly contacted with the ascending vapors, serving to partially cool said vapors, and, in turn, being thereby preheated. y

Other and further objects and advantages of the invention will become apparent from the following description and attached diagrammatic drawing, illustrating one form of apparatus in which the invention may be carried out.

Referring to the drawing, raw oil charging stock may be supplied through a line I, controlled by a valve 2, and fed via a pump 3, through aline li, controlled by a valve 5, into an absorber 6, passing therethrough in a general downward direction, countercurrent to and in direct contact with incondensable gases from the system. The raw oil charging stock, together with any absorbed light liquid products stripped from the gases, may pass through a line 'I,c0ntrolled by a valve 8 from absorber 6, to a pump 9, from which it may be fed through a line I0, controlled by a valve I I to a fractionator i 2. The raw oil may be further preheated in fractionator I2 by direct contact with the vapors being treated therein, serving, at the same time, to cool the latter and assist in their fractionation. The preheated raw oil charging stock, together with relatively heavy components of the vapors which may be condensed in fractionator I2 may pass through a line i3, controlled by a Valve I4 to a pump I5, which may supply the combined feed of raw oil and relatively heavy, condensed components, through a line I5, controlled by a valve Il, to a heating element I8 of any conventional type.

A secondary charging stock, preferably a distillate of relatively lighter gravity and more refractory to cracking than the primary charging stock, may be supplied through a line I9, controlled by a valve 20, to a pump 2 I, and may thence be fed through a line 22, controlled by a valve 23, into said line I6, wherein it may combine with the preheated primary charging stock and reflux condensate from fractionator I2 and may be passed therewith to said heating element I8.

Heating element I8 may be disposed in any suitable type of furnace 24, and the oil passing therethrough may be heated to any desired conversion temperature, preferably under a substantial super-atmospheric pressure. The heated oil may be discharged from said heating element through a line 25, controlled by a valve 26, and

introduced into a chamber 21 wherein vapors and unvaporized oil may separate.

Chamber 21 may be maintained under substantially the same or a lower pressure than that existing in heating element I8, but should, in all cases, be sufficient to overcome the frictional resistance offered to the flow of vapors from said chamber to and through a secondary heating element 28. Vapors may be withdrawn from chamber 21 through a line 29, controlled by a valve 38, and introduced into said secondary heating element 28, which may be disposed in any suitable type of furnace 3l.

After introduction into secondary heating element 28, said vapors may be subjected to reconversion conditions of temperature and pressure therein, preferably of. a more severe order than the conversion conditions maintained in heating element I8. The reconverted vapors may be discharged from heating element 28 through a line 32, controlled by a valve 33, into a chamber 34. After their passage through valve 33 in said line 32, the pressure on the reconverted vapors may be preferably substantially reduced, said chamber 34 being maintained under a substantially reduced pressure relative to that existing in chamber 21. Unvaporized oil may be withdrawn from chamber 21 through a line 35, controlled by a valve 36, and passed into a line 31, communicating with line 32 through which the reconverted vapors may pass. Said line 31 preferably communicates with line 32 on the low pressure side of valve 33 interposed in line 32, and I am thus enabled to effect a commingling of the unvaporized oil from chamber 21 with the reconverted vapors passing through line 32 from said secondary heating element 28, and passing in such commingled state into chamber 34, thereby effecting a cooling of said reconverted vapors within said line 32. Unvaporized residual oil may be withdrawn from chamber 34 through a line 38, controlled by a valve 39, and subjected to cooling in a cooler 4l), and thereafter passed through a line 4i t0 pump 42, from which it may be fed, as desired, in part through a line 43, controlled by a valve 44, and line 31 to said line 32, to commingle in said line 31 rst with unvaporized oil from chamber 21 to effect a cooling thereof, and passing therewith to line 32 wherein it may commingle with reconverted vapors from heating element 28 serving as a further cooling media for the reconverted vapors passing to chamber 34. The remainder, if any, of the cooled residual oil withdrawn from chamber 34 may pass via pump 42, line 43, control valve and line 46 to storage or elsewhere, as desired.

Vapors from chamber 34 may pass through a line 41, controlled by a valve 48, to a fractionator I2 where their relatively heavy insufficiently converted components may be condensed and returned to heating element I8 for reconversion, as already described. Fractionated vapors of the desired composition, preferably boiling within the range of commercial motor fuel, may pass from fractionator I2 through a line 49, controlled by a Valve 58, and be subjected to condensation and cooling in a condenser 5|. Condensed distillate and incondensable gases from said condenser 5I may pass through a line 52, controlled by a valve 53, to a receiver 54 for collection. Distillate may be withdrawn from receiver 54 through a line 55, controlled by a valve 5S. A portion of the distillate may, if desired, be withdrawn through a line 51, controlled by a valve 58, to a pump 58 and recirculated via line 60, controlled by a valve 6l, through fractionator l2 to assist in fractionation of the vapors under treatment therein. Gases may be released from receiver 54 through a line 62, controlled by a valve 83, and passed via pump or compressor 8G and a line 61, controlled by a valve 68, to absorber 8, where they may be substantially stripped of any entrained light liquid hydrocarbons by direct contact with the raw oil charging stock for the system introduced into this zone, as previously described, Pump 56 may, of course, be dispensed with in oase absorber 6 is operated under substantially the same or a lower pressure than that employed in receiver 54. Stripped incondensable gases may be released from absorber 6 through a line 64 controlled by a valve B5.

Pressures employed within the system may range from subatmospherc to superatmospheric pressures as high as 2000 pounds or more per square inch. element and the primary enlarged zone or chamber are maintained under a substantial superatmospheric pressure of the order of 100 to several hundred pounds or more per square inch. The pressure may be substantially equalized between these two elements, or a reduced pressure may be employed in the primary chamber or separator. The secondary heating element, and the secondary enlarged chamber or evaporator may be maintained under substantially atmospheric, subatrnospheric or superatmospheric pressure. Preferably, however, a substantial superatmospheric pressure may be maintained in the secondary heating element, while the chamber 34 may be maintained at a relatively reduced pressure to that employed in said secondary heating element. The fractionating, condensing and collecting portions of the system may be maintained under substantially the same or lower pressures than that employed in the chamber 34. The absorber may preferably be operated under a superatmospheric pressure, although substantially atmospheric or sub-atmospheric pressures may be employed, if desired.

Conversion temperatures employed within the system may range from '750 to 1200 F., more or less. Preferably, milder conversion conditions may be employed in the primary heating element than those to which the vapors may be subjected in the secondary or vapor-phase heating element.

As one specific example of an operation employing the principles of the invention, a Sii-38 A. P. I. gravity fuel oil primary charging stock, comprising about 85% of the total charging stock fed to the system (the remaining 15% or thereabouts being a water-white distillate from Pennsylvania crude, having a gravity of about 48 A. P. I., and of relatively narrow boiling range), is fed, in combination with reflux condensate from a. fractionator, to a primary heating element and subjected to a temperature of about 875 F., under a superatmospheric pressure of about 350 pounds per square inch. The resultant vapors are subjected to reconversion in a secondary heating element at a temperature of about 1000 F., under a pressure of approximately 200 pounds per square inch. The pressure in a secondary enlarged chamber into which the reconverted vapors are discharged, is reduced to about 30 pounds per square inch. and a substantially equalized pressure of about this order is maintained on the succeeding portions of the system, including the absorber. As a result of this operation, a yield of Preferably, the primary heating a some '70% of premium motor fuel, having an anti- 76 knock value equivalent to a blend of approximately 50% benzol and 50% straight-run Pennsylvania gasoline may be obtained. About 22% of a good quality residual oil, suitable for sale as fuel may be the only other liquid product from the process, while the gases produced may be of high caloric value, substantially free of entrained light liquid components, and may be suitable for blending with gas of lower B. t. u. content to improve the quality of the latter.

By increasing the conversion temperature in the secondary or vapor-phase heating element, the anti-knock value of the motor fuel may be increased, but this. however, may result in a somewhat lower yield of motor fuel and an accompanying increased yield of gases.

When it is desired to operate the process on a nonresiduum basis, that is, without the production of residual products, conditions may be so regulated within chamber 34 that the residual products produced therein may be substantially dry carbonaceous material which may accumulate within said chamber and may be removed therefrom upon the operation being discontinued; or, if desired, a plurality of such chambers (not shown) may be utilized, either alternately or simultaneously to effect a prolonged operation. In event a non-residuum operation is employed, no residual liquid may be produced in chamber 35 after the desired operating conditions are obtained, and, therefore, no liquid may be recycled from this zone to line 32, as previously described. Residual liquid from chamber 21, however, may be introduced into said line 32 in both a residuum and non-residuum type of operation.

I claim as my invention:

1. A process for cracking hydrocarbon oils, which comprises charging crude oil through incondensable gases previously removed from the system, passing said oil, together with condensed portions removed from said gases to a fraction-- ator to combine reux condensate therewith and to revaporize said condensed portions therefrom, passing the resultant mixture to a heating zone wherein conversion conditions of temperature and pressure are maintained, discharging the resultant heated products into a reaction zone where liquids and vapors separate, subjecting the vapors to reconversion in a secondary heating zone, passing the reconverted products to a zone of reduced pressure, withdrawing the heavier, insuiciently converted components from said zone of reduced pressure, cooling the same, combining said cooled, insufficiently converted components from said zone of reduced pressure with heavier portions withdrawn from said reaction zone, commingling the resultant mixture with the reconverted products withdrawn from said secondary heating zone prior to their introduction into said zone of reduced pressure, supplying vapors from said zone of reduced pressure to said fractionator for fractionation therein, finally condensing the fractionated vapors? and separating resultant distillate from incondensible gases, and scrubbing the latter with the crude oil as aforesaid.

2. A hydrocarbon oil cracking process which comprises passing the oil through a heating Zone and heating the same therein to cracking temperature under pressure, discharging the heated oil into a vapor separating zone and separating the same therein into vapors and unvaporized oil, removing separated vapors from the separating zone and heating the same to vapor phase cracking temperature in a second heating zone maintained at higher temperature than the firstmentioned heating zone, separately removing unvaporized oil from, the separating zone and commingling the same with hot vapor phase cracked vapors from said second heating Zone, separating the resultant mixture into vapors and residual oil, cooling at least a portion of said residual oil and commingling the same with said hot vapor phase cracked vapors from the second heating zone.

3. The method of treating hydrocarbon oils to convert higher boiling hydrocarbon oils into lower boiling hydrocarbons that comprises topping fresh charging stock in a heating and separating zone separate and apart from the cracking, separating and fracticnating zones hereinafter specified by heating in a heating coil a flowing stream of the fresh charging stock to a tem,- perature adequate to effect substantial vaporiZation and by discharging the heated oil into a separating zone wherein separation of vapors from unvaporized oil takes place, withdrawing the vapors from said separating Zone and passing them to a vapor phase cracking Zone wherein said vapors' are heated to a vapor phase cracking temperature and subjected to cracking, discharging the cracked products from said vapor phase cracking zone into a second separating Zone wherein vapors separate from residue, passing said vapors last mentioned to a fractionating zone and subjecting the vapors to fractionation therein to form fractionated vapors and reflux condensate, condensing the fractionated vapors as a desired product, conducting reflux condensate formed in said fractionating zone to aforesaid heating coil, passing said unvaporized oil from aforesaid separating zone into said second separating Zone and delivering a cooling liquid, comprising liquid constituents separated out in said second separating zone, into direct contact with said cracked produtcs passing from said vapor phase cracking zone to said second separating zone.

LYMAN C. I-IUFF, 

